1995 Volume 1995 Issue Supplement83 Pages 1-11
This study examined the topographical relationships of the loop of the anterior inferior cerebellar artery (AICA) to the cochleovestibular (VIII) nerve in the internal auditory canal (IAC) using histopathological methods involving three-dimensional reconstruction to clarify the cause and pathogenesis of neurovascular compression (NVC) of the VIInIe rve.
The AICA loop within the IAC was found in 50 of 356 autopsied human temporal bones examined histopathologically at the hospital of Fukushima Medical College. Thirty-three of the 50 temporal bones, which were well preserved, were observed by histopathological three-dimensional reconstruction. In addition, histological sections from 33 of the 50 temporal bones, which showed neither hemorrhage nor malignant tumor cell infiltration in the IAC, were stained with Kluver-Barrera's, Bodian's and Masson's methods and observed under light microscopy.
The temporal bones were grouped into two main classes by three-dimensional location of the AICA, VIIa nd VIII nerves in the IAC, the inter-nerve and the extra-nerve types. Twenty-four temporal bones with loops of the AICA located between the VII and VIII nerves were considered the internerve type, and 9 specimens with the loops of the AICA located outside the two nerves were considered the extra-nerve type.
In 23 of 33 temporal bones examined, the loop of the AICA was located at the Glia-Schwann sheath junction of the VIII nerve or more peripherally.
Demyelination of the VIII nerve and atherosclerosis of the AICA were found in 10 and 11 of 30temporal bones examined, respectively.
These morphological findings are discussed with special reference to NVC of the VIII nerve.
